1. Field of the Invention
The present invention relates to an internal combustion engine installed in an engine compartment covered with an engine cover. The invention relates more specifically to a structure including the engine cover and an air intake part of the engine. The engine is used typically in marine propulsion machines, for example, outboard motors.
2. Description of the Related Art
A typical outboard motor has an internal combustion engine housed in an engine compartment defined by an engine cover. If an intake air inlet of the intake system of the engine opens into the engine compartment, air to be sucked for combustion into the engine will be heated by the heat generated in the engine and sucked into the engine as heated combustion air. As a consequence, the charging efficiency of the engine will be lowered with resultant reduction in engine output. JP 59-120598 A and JP 05-286490 A disclose a technique for improving the charging efficiency, in which it is attempted to suck air outside the engine compartment into the engine.
When the intake air inlet of the intake system of the engine is in communication with the engine compartment, the air pressure within the engine compartment is caused to vary due to intake pulsation of the engine, and the varying air pressure causes the engine cover to vibrate with resultant generation of noises. The vibration can be prevented by providing a sealing member that shuts off communication between the interior of the engine compartment and the intake air inlet of the intake system. In case the sealing member is to be fixedly secured between members which are adjacently disposed in the direction of flow of the combustion air in the intake air inlet, it is required to increase the dimensional accuracy of the adjacent members with respect to the flow direction of the combustion air, for the purpose of providing a reliable sealing property and required sealing forces in the flow direction of the combustion air. Moreover, the sealing property is susceptible to the influence of the vibration since the intake system and the engine cover are caused to vibrate due to the engine operation.
The present invention has been made in view of the above circumstances, and it is an object of the invention to provide a sealing structure between the engine cover and the intake air inlet of the intake system, in which a high dimensional accuracy is not required to secure a required sealing property and in which the sealing property is not susceptible to the influence of the vibration. It is a further object of the invention to provide a sealing structure which can be easily assembled between the engine cover and the intake air inlet of the intake system, by utilizing a position determining means on the engine cover made up of divided cover elements.